1. Field of the Invention
The present invention relates to a hearing aid apparatus, and in particular to a hearing aid apparatus adapted for use in aural training systems.
2. Description of the Prior Art
In conventional hearing aid devices such as described, for example, in U.S. Pat. No. 4,137,431, terminals for electrical signals are employed for the introduction of signals from an external microphone, such as an external microphone in a telephone handset or a microphone which is part of an aural training apparatus. Audio signals from other signal generators such as radio and television receivers may also be directly introduced into the hearing aid apparatus by means of such leads.
If the hearing aid apparatus is connected to an aural training apparatus, however, it is still necessary to utilize a separate microphone for picking up the speech of the other students in the room with the user. In conventional systems, this is accomplished by station amplifiers installed at each trainee station. This requires a rather complicated network which must be provided for every trainee station.